Usually August 1 is the beginning of the end of the season of noctilucent clouds in the Northern Hemisphere. Weather conditions in the upper atmosphere of the Earth change in August, which makes it difficult to form them.
Soon after, the noctilucent clouds disappear from the field of vision. However, August has already begun, and noctilucent clouds can still be seen. Vesa Vauhonen took this picture in Rautalampi, Finland.
According to her, the morning of August 1, the most beautiful silvery clouds that she had seen over the lake of Konnevesi appeared over the lake.
Noctilucent clouds are formed when summer water vapor rises to the top of the atmosphere and envelops meteor smoke, forming ice crystals.
In 2017, a thermal wave in the mesosphere melted these crystals, which led to a short period of absence of noctilucent clouds. Could it be that something like this, but the opposite of the action occurred at the end of the season of noctilucent clouds? Perhaps the cooling in the mesosphere extended the season?
Another possibility is the solar cycle. Previous studies have shown that noctilucent clouds can sometimes become more intense during the solar minimum. At present, such conditions are in effect – in recent months the activity of the Sun has fallen to zero.